In newspaper printing processes and the like, the paper web with the print thereon is heated to fix the ink. The heating temperature is very high, close to the scorching temperature of the paper, so it is desirable to quickly chill the newsprint web after the ink has been appropriately heated
Water cooled chill rollers are well known to the art. The water is first cooled by a refrigeration system, and is then pumped into the hollow chill roller, which is made of a conductive material such as steel or aluminum. Thus, the hot web passes across the rotating chill roller and is cooled, while the chill roller is cooled by the water (typically brine) present within the chill roller.
It has been found that this system exhibits some significant difficulties. First, the heat exchange between the water and the interior of the chill roller takes place by conduction and convection. Neither of these processes are fast, so it has been necessary to use quite cold water to provide adequate heat absorbing characteristics to the system. The problem is made worse by the fact that the water can deposit lime on the inside of the chill roller unless it has been deionized, which is of course an added expense. The lime deposit on the inner wall of the chill roller provides an insulating layer, which requires even colder water to be used. Because of the very cold water present in the roller, water condensation can take place in areas of the chill roller that the hot news print web does not contact. This is of course a great disadvantage, since the newsprint web disintegrates in the presence of water.
Also, if it is necessary to stop the rotation of the chill roller, it quickly cools down and begins to condense water or "sweat" over substantially all of its surface, which can result in that much faster disintegration of the newsprint web.
Accordingly, while prior art water cooled chill rollers are used for lack of a better system, they exhibit significant drawbacks and difficulties. By this invention, the above difficulties are reduced or eliminated.